1. Field of the Invention
The present invention relates to an inkjet printer for recording an image on a recording medium.
2. Description of the Related Art
Inkjet printers are widely used. An inkjet printer ejects ink from an inkjet recording head onto a recording medium to record an image. Ink stored in an ink cartridge is supplied to the recording head. Printers of this type include not only small-sized household printers for recording onto an A4 or A3 size sheet, but also large-sized printers capable of printing onto a wide recording medium having a width of 1 m or greater.
Inks used for recording include various types of inks, such as an ink obtained by dissolving dye in a solvent such as water, a solvent ink obtained by dispersing a pigment in an organic solvent, an ultraviolet curable ink that is cured by ultraviolet rays, and a heat curable ink that is cured by heat.
An inkjet printer includes a carriage on which a recording head is mounted. The carriage reciprocates in a width direction of a recording medium, i.e., main scanning direction. The recording head ejects ink onto the recording medium on a forward path and a backward path to record an image. The recording medium is conveyed in a direction perpendicular to the moving direction of the carriage, i.e., a sub scanning direction. The inkjet printer conveys the recording medium by a predetermined amount at one time, and ejects ink while moving the carriage in the main scanning direction. This operation is repeated to record an image. The predetermined amount is equal to an amount obtained by dividing the length of the recording head by an integer of 2 or greater. A position of the carriage is detected by reading a linear scale disposed along the moving direction of the carriage by means of a sensor mounted on the carriage. Typically, a device called a linear encoder is used. The inkjet printer includes a flat-plate platen having a width equal to or greater than a length of a nozzle array of the recording head. The inkjet printer causes the recording medium to be absorbed on the platen and keep flat, and ejects ink onto the recording medium, thereby recording an image. The inkjet printer keeps a recording medium flat and ejects ink onto the flat recording medium based on the position of the carriage measured by the linear encoder, so that it can record an image under stable conditions, thereby recording an image having high quality.
However, the recording medium supported by the platen may have a wrinkle, which may deteriorate quality of the recorded image, damage the recording head, or cause jam of the recording medium.
For example, Japanese Patent Application Publication No. 2012-228778 discloses a device including an ink head moving in a main scanning direction perpendicular to a conveying direction of a recording medium, a rotating member rotatably fixed, and a detection unit provided to the ink head and configured to detect rotation of the rotating member. The device detects proximity of a recording medium to the ink head by detecting rotation of the rotating member due to contact with the recording medium. If rotation is detected by the detection unit, the device stops movement of the ink head, thereby preventing the ink head from being damaged.
The above device detects, by detecting rotation of the rotating member, that the distance between the ink head and the recording medium has become equal to or less than a predetermined value, and performs processing such as stopping.
However, the rotating member is fixed near the ink head, so splattered ink or ink mist may adhere to a rotating part of the rotating member. If ink adheres to the rotating part, the ink may increase the force required to rotate the rotating member, or at worst, may solidify and lock the rotating member. These may cause erroneous detection or disable the detection. Control based on erroneous detection of the rotating member may cause fatal damage to the recording head.